According your problem that some functions, which were derived via symbolic evaluation, are considered "not defined" when later used numerically:
The cause is that with the symbolic evaluation the units loose their label "Unit" and are treated as unknown variables and so a later numeric evaluation fails.
To cope with this problem PTC has implemented the option "Units/Constants in Symbolics" in the Calculation Options.
You should turn on this option and then recalculate the worksheet.

Actually I don't understand why this option is not turned on per default.
Your unit problem is based an the fact, that your parameter t is used dimensionless and not as dimension time.
That way integration over t does not change the unit and your velocity and displacement are still of dimension acceleration.
You may correct this by multiplying the definition of v and S by seconds (see attached worksheet), but IMHO the better approach would be to use t as time throughout which also means that you would have to write something like sin(t/s) instead of sin(t) or sin (omega t) with omega as frequency.
